Process for treating polluted soils by means of a sulfoaluminate clinker based hydraulic binder and use thereof for stabilizing polluted soils

Abstract

A process for treating polluted soils, in particular soils with a leachable fraction greater than 0.4%, wherein the leachable fraction contains predominantly anions, in particular sulfate ions, and/or heavy metals, includes mixing the soil with a sulfoaluminate-clinker-based hydraulic binder, in soil/binder weight proportions of between 1 and 40 parts of binder per 100 parts of soil, the sulfoaluminate clinker containing more than 50% by weight of ye'elimite C 4 A 3 S phase, less than 15% by weight of belite C2S phase, and from 1% to 5% by weight of free lime CaO. The process is used for stabilizing soils in situ or before dumping, soils polluted in particular with sulfate anions and/or heavy metal cations.

The invention claimed is: 
     
       1. A process for the treatment of polluted soils, in particular of soils exhibiting a leachable fraction of greater than 0.4%, said leachable fraction predominantly including anions sulfate ions, and/or heavy metals,
 wherein said process comprises the mixing of said soil 
 with a hydraulic binder based on sulfoaluminate clinker in soil/binder proportions by weight of between 1 and 40 parts of binder per 100 parts of soil, said sulfoaluminate clinker 
 including more than 50% by weight of ye'elimite C4A3$ phase, less than 15% by weight of belite C2S phase and from 1% to 5% by weight of free lime CaO, and wherein 
 
       said sulfoaluminate clinker includes from 2% to 12% by weight of mayenite C 12 A 7  phase or of a mayenite isotype. 
     
     
       2. The treatment process as claimed in  claim 1 , wherein the sulfoaluminate clinker includes more than 60% by weight of ye'elimite C4A3 $ phase. 
     
     
       3. The treatment process as claimed in  claim 1 , wherein the sulfoaluminate clinker includes from 5% to less than 15% by weight of belite C2S phase. 
     
     
       4. The treatment process as claimed in  claim 1 , wherein said process comprises the mixing of said soil with the hydraulic binder in soil/binder proportions by weight of between 1 and 20 parts of binder per 100 parts of soil. 
     
     
       5. The treatment process as claimed in  claim 4 , wherein said process comprises the mixing of said soil with the hydraulic binder in soil/binder proportions by weight of between 5 and 20 parts of binder per 100 parts of soil. 
     
     
       6. The treatment process as claimed in  claim 1 , wherein the hydraulic binder is composed solely of a sulfoaluminate clinker including more than 50% by weight of ye'elimite C4A3 $ phase, less than 15% by weight of belite C2S phase and from 1% to 5% by weight of free lime CaO. 
     
     
       7. The process as claimed in  claim 1 , wherein said hydraulic binder does not include a setting accelerator. 
     
     
       8. The process as claimed in  claim 1 , wherein said hydraulic binder includes at least 20% by weight of said sulfoaluminate clinker and one or more compounds chosen from cement, Portland clinker, lime, a filler, admixtures having a pozzolanic effect, and optionally one or more additives. 
     
     
       9. The process as claimed in  claim 8 , wherein said hydraulic binder includes quick lime in an amount of less than 50% by weight. 
     
     
       10. A process for the stabilization of soils, which soils are polluted in particular by sulfate anions and/or heavy metal cations, said process comprising the steps of:
 mixing said soils with a hydraulic binder based on sulfoaluminate clinker in soil/binder proportions by weight of between 1 and 40 parts of binder per 100 parts of soil, said sulfoaluminate clinker including more than 50% by weight of ye'eliminate C4A3$ phase, less than 15% by weight of belite C2S phase and from 1% to 5% by weight of free lime CaO and from 2% to 12% by weight of mayenite C 12 A 7  phase or of a mayenite isotype, 
 wherein said mixing is either one of in situ in the soil to be treated or said mixing is performed with said soil prior to landfilling. 
 
     
     
       11. The process as claimed in  claim 10  wherein the soil prior to treatment has a water content of less than 40% by weight. 
     
     
       12. The process as claimed in  claim 10 , wherein said method further includes the step of depositing said soil, treated by said process in road bases or backfills. 
     
     
       13. The treatment process as claimed in  claim 3 , wherein the sulfoaluminate clinker includes from from 8% to 13% by weight of belite C2S phase. 
     
     
       14. The treatment process as claimed in  claim 1 , wherein the sulfoaluminate clinker includes from 2% to 3% by weight of mayenite C 12 A 7  phase or of a mayenite isotype. 
     
     
       15. The treatment process as claimed in  claim 4 , wherein said process comprises the mixing of said soil with the hydraulic binder in soil/binder proportions by weight of between 2 and 20 parts of binder per 100 parts of soil. 
     
     
       16. The treatment process as claimed in  claim 5 , wherein said process comprises the mixing of said soil with the hydraulic binder in soil/binder proportions by weight of between 5 and 10 parts of binder per 100 parts of soil. 
     
     
       17. The process as claimed in  claim 8 , wherein said hydraulic binder includes at least 30% by weight of said sulfoaluminate clinker and one or more compounds chosen from cement, Portland clinker, lime, a filler, admixtures having a pozzolanic effect, and optionally one or more additives. 
     
     
       18. The process as claimed in  claim 11  wherein the soil prior to treatment has a water content of less than 30% by weight.